1. Field of the Invention
The present invention relates to a digester tank construction for use in digestion systems for the anaerobic digestion of waste water sludge.
2. Prior Art
Various tanks incorporating interior movable diaphragms have been advanced in the art, and generally such diaphragms have been for following the level of liquid in a tank.
Examples of the prior art include U.S. Pat. No. 2,696,185 which shows a barge that has membranes dividing the barge into different tanks and which vary the volume of each of the tanks as liquid is either added or taken out of the respective tank.
U.S. Pat. No. 3,537,608 shows a fluid storage tank for storing two fluids of variable volume, for example oil and gasoline. U.S. Pat. No. 3,477,611 has a diaphragm which separates the atmosphere from the contained product and combines liquid and gas vapor from the contained product in one chamber, but provides no means for establishing a constant desired pressure. The device allows for a range in pressure with relief to the atmosphere coming only when the pressure achieves a certain level. U.S. Pat. No. 21,761 is a keg which has an interior lining that permits an air pocket to form behind the linear to divide the keg into two chambers.
U.S. Pat. No. 2,578,090 shows a diaphragm that is in contact with the level of liquid as the liquid varies in volume inside the container, and U.S. Pat. No. 2,670,100 also shows an adjustable diaphragm that adjusts itself to varying volumes of liquid and which may move off the top of the liquid when a generated gas is present.
Other examples of prior patents showing diaphragm type tanks include U.S. Pat. Nos. 1,716,950; 2,136,202; 3,749,165; and 3,902,624.